BELL. — ULTRAVIOLET COMPONENT IN ARTIFICIAL LIGHT. 21 



tube; quartz lamp of the French Cooper Hewitt Company without 

 globe; quartz lamp, i\merican, without globe; quartz lamp, American, 

 with globe; Graetzin mantle burner; acetylene flame; carbon electric 

 arc through quartz window; magnetite arc through quartz window; 

 magnetite arc with ordinary globe; Nernst glower. In addition, a 

 study was made of sunlight witli the thermopile for comparative 

 purposes and spectrographic studies were also made of the ordinary 

 yellow flame arc and of the arc between iron terminals such as is used 

 for therapeutic purposes. The Euphos glass was chosen as the 

 medium for the partition of the ultra violet from the rest of the spec- 

 trum for the reason that it cuts out and was intended to cut out by 

 its designers all the rays of any illuminant which are under indictment 

 as having specific harmful action on the eyes. 



Broadly, the accusations of short wave lengths as injurious to the 

 eye involve the entire ultra violet from the furthest point reached by 

 natural or artificial illuminants up to and into the chemically active 

 rays of the violet. If on the one hand it is the rays in the extreme 

 ultra violet, wave length 300 jjifx and less, which are absorbed by the 

 cornea, that are held responsible for the ordinary phenomena of 

 ophthalmia elcdrica, it is the rays of ultra violet of greater wave length 

 than this, extending clear into the violet, that have been regarded 

 by some recent investigators as producing perhaps serious lesions of 

 the retina and of the lens. Note Schanz and Stockhausen.^^ The 

 former class of injuries which have to do with the radiations absorbed 

 by the cornea are wholly superficial and, according to Van Lint ^^ the 

 prognosis is generally good and the recovery rapid. Injuries to the 

 retina and the lens, in-so-far as they take place, involve a far greater 

 danger of permanent injury. Glass-blowers cataract is one of the 

 typical injuries which has been ascribed to ultra violet radiations lying 

 adjacent to the visible spectrum by Schanz and Stockhausen, Birch- 

 Hirschfeld and others. Obviously, the temperature of melting glass 

 (1400° C) is too low to give rise to any material amount of energy in 

 the extreme ultra violet. 



The present investigation, therefore, took account of the whole 

 body of radiations of short wave length. So far as possible injury 

 from the ultra violet component in any artificial light source is con- 

 cerned it is obviously dependent on the amount of actual energy 

 delivered by the source in the ultra violet region and not upon the 



15 Ztschr. f. Augenheilk., Mai, 1910. 



1® Accidents oculaires provoque's par I'electricite, p. 100. 



